They don't really do enough with the summons for a summoner.

It's basically no different then black magic.

Maybe if they had other uses then simply group casts they could be awesome.

FF X did the combat with them, which was a neat Idea, but not executed very well. They didn't have a big variety of what they could do, and they were pretty overpowered.

Perhaps you could call Summons either into yourself altering your stats and abilities, kind of like the Persona main characters? Not to the extreme that persona goes mind you, but having a character that can infuse himself with a variety of creatures like that could be fun.